I think this is a larger problem in how scripted and lazy BG3 is in this regard.
It's very stupid of the Shadow Druids to attack at the core of a hostile Grove in the first place. When exposed, why don't they just escape as rats or birds, and then later ambush the party in the woods on their terms?
Larian seem to be opposed to addìng events like this the player can't prepare for and metagame the challenge out of. God forbid the player is inconvenienced in such a way that would actually put some challenge and unexpected elements into the game. And that's exactly what this game needs.Vengeful Shadow Druids ambushing the party at camp at night, or at some random location when the party is not expecting them. Shadow Druids that act wisely and in character help the world become more convincing and keep the player on their toes.